A global navigation satellite system typically refers to a device which receives a satellite signal from an artificial satellite revolving around the Earth and which calculates a location of a given device based on the received satellite signal. However, since the number of observable satellites is reduced in environments where signals of satellites are interrupted (e.g., built-up areas, tunnels, underground parking lots, etc.), positioning errors are often caused. Positioning accuracy may be reduced, or may become entirely impossible.
Various techniques, such as fusing dead-reckoning, may be employed to compensate for the potential of interrupted satellite signals. A separate device for providing coordinates of a corresponding location may be utilized in areas where signals of satellites are interrupted. Methods for receiving location coordinates from such a device may also be used.
However, if a current location of the device differs from the coordinates actually received, current location information may become inaccurate. Additional devices installed in areas where satellite signals are interrupted result in a waste of both time and money.
Meanwhile, airplanes, fighter planes, or the like use an expensive inertial measurement unit (IMU) for dead-reckoning. Vehicles and robots may calculate their locations through time integration using information acquired from sensing devices such as a wheel encoder, a speedometer, and a yaw rate sensor.
Even when satellite navigation and dead-reckoning are combined, a position error may increase over time. This may be generated by an accumulation of errors of the IMU itself. As performance of an IMU improves, the likelihood of position error by dead-reckoning may be more reduced. However, in this case, the overall price of a system may be increased due to the use of expensive IMU sensors.